Organic compounds can take various structures compared with inorganic compounds, and can be used to synthesize a material having a variety of functions with appropriate molecular design. Because of these types of advantages, attention has been focused on photo electronics and electronics in which functional organic compounds are used in recent years.
For example, as examples of electronic devices in which organic compounds are used as functional organic materials, there are solar cells, light-emitting elements, organic transistors, and the like. These devices use the electrical properties and optical properties of organic compounds. Among them, in particular, tremendous progress has been made in light-emitting elements.
It is said that the light emission mechanism of a light-emitting element is as follows: by application of a voltage between a pair of electrodes with a light-emitting layer interposed therebetween, electrons injected from a cathode and holes injected from an anode recombine in the luminescence center of the light-emitting layer to form excitons in molecules, and when the excitons in molecules relax to a ground state, energy is released to emit light. A singlet excited state and a triplet excited state are known as excited states, and it is thought that light emission can be obtained through either of the excited states.
In an attempt to improve the properties of such a light-emitting element, there are many problems depending on a material. In order to solve these problems, improvement of an element structure, development of a material, etc. have been carried out.
For example, in Patent Document 1, an anthracene derivative that emits green light is disclosed. However, in Patent Document 1, only the PL spectrum of the anthracene derivative is disclosed, and the properties of a light-emitting element to which the anthracene derivative is applied are not disclosed.
Further, in Patent Document 2, a light-emitting element using an anthracene derivative for a charge-transporting layer is disclosed. However, in Patent Document 2, there is no description of the lifetime of the light-emitting element.
In view of commercialization, an increase in lifetime is an important object, and development of a light-emitting element having better properties is desired.
[Patent Document 1]
United States Patent Application Laid-Open No. 2005-0260442
[Patent Document 2]
Japanese Published Patent Application No. 2004-91334